Fuel for internal combustion engines is usually filtered first before it is fed to the actual combustion process. The water contained in the fuel can damage the internal combustion engine itself or parts thereof, such as an injection system, for example by oxidation of metal parts, for which reason fuel filters are usually used, which are intended to filter out the highest possible proportion of the water contained in the fuel. In known fuel filters, a water collection chamber is arranged in the lower region, in which chamber the water collects owing to its higher specific density compared to fuel. At predefined times, or when predefined levels are reached, the water collection chamber is emptied and the water situated therein is drained. The disadvantage of known fuel filters is however that contamination of the environment with fuel can occur if a water discharge device for draining the water from the water collection chamber incorrectly detects a water level.